The nose is a complicated structure that serves dual functions as the organ for the sense of smell and as an entry to the respiratory tract. As part of the respiratory tract, a healthy nose moisturizes and warms incoming air and filters out foreign materials.
Nasal passages and other portions of the respiratory tract are lined with specialized tissue layers. In the nose and sinus areas this tissue is often called the nasal mucosa. Like many tissues, the nasal mucosa is composed of several cell layers and cell types. Mucous cells are one type of cell found in the nasal mucosa. These cells are found throughout the nasal mucosa and are generally clustered into small glands. These glands secrete a sticky substance called mucus. Mucus is composed of water, shed epithelial (surface) cells, dead leukocytes, mucin, and inorganic salts, among other things, that are all held in suspension. Mucus functions as a trap for airborne particles (e.g., dust, bacteria, and viruses) that enter the nasal passages. Mucus also lubricates the walls of the nose, sinuses, and throat.
In a healthy nose, the mucus is cleared from the nasal passages on a regular basis by a layer of cells in the nasal mucosa called the ciliated columnar epithelium. These cells possess small hair-like projections called cilia that undulate and “sweep” mucus through the nasal passages allowing it to drain to the back of the throat where it can be swallowed or expelled. This line of defense protects the body against the bacteria and viruses that continually enter the nose and mouth.
Connected to the nose are sinuses or air-filled cavities located behind certain facial bones. There are four groups of sinuses, namely, frontal, sphenoidal, ethmoidal, and maxillary. The sinuses are also lined with mucus secreting tissue. The sinuses are normally kept clear when mucus drains through them into the nasal passages. However, under low humidity atmospheric conditions typically found on airplanes and in desert areas, the sinuses can become dry resulting in nasal discomfort.
Nasal sprays have been commercially available for moisturization of the nasal membranes. Such sprays normally are water containing surfactants to spread the water over the nasal membranes and enhance the penetration of the water into the surface layers of the membranes. There is no therapeutic function of the water penetration.
Therefore, it would be advantageous to provide a hypotonic or isotonic saline solution for a nasal spray or nasal drop solution that includes a lubricating agent and an anti-microbial agent for moisturizing the nasal passages and lessening or alleviating nasal dryness.